Neutron diffraction determination of the microscopic structure of solid deuterium close to melting

The static structure factor of solid normal deuterium, close to its triple point, has been measured usingtime-of-flight neutron diffraction. Experimental results have been compared to path-integral Monte Carlosimulations as well as to a simple uncorrelated lattice calculation including the mean-squared displacement asan adjustable parameter. We found a very good agreement between experimental data and quantum simulationsin all the measured range, while the uncorrelated model, as expected, turned out to be satisfactory only at longdistances and for a mean-squared displacement value almost twice as large as the low-temperature one. Thisfact can be ascribed to the large anharmonic character of the D2 quantum crystal close to its melting.